During production processing of metals, such as steel, rolling of the metal is followed by controlled cooling. During the production processing, particularly the cooling process, a microstructure of the metal evolves and results in a final microstructure of the processed metal. The microstructure of the processed metal has an impact on many aspects of the metal's character, such as tensile strength.
Conventional microstructural analysis techniques are destructive and involve removing samples for analysis from, for example, the end of a coil of the processed material. This is time-consuming, costly, does not allow continuous monitoring, and assesses only a small fraction of the material processed.
When the processed material is steel, it is known that electromagnetic techniques can monitor steel phase transformations by detecting the ferromagnetic phase change due to the changes in electrical conductivity and magnetic permeability within the steel. Furthermore, if a coil is placed in the vicinity of the steel being processed, this results in a change in impedance measurements for the coil because conductivity and permeability are influenced by the steel's microstructure. For example austenite, the stable phase of iron at elevated temperatures, is paramagnetic whereas the stable low temperature phases ferrite, pearlite, bainite and martensite are ferromagnetic below the Curie temperature of about 760° C. Steel properties vary strongly with the volume fractions of these phases, which are controlled largely by the cooling rate and alloy content of the steel.
However, problems exist in monitoring in real-time the electromagnetic properties of metals during processing. Many problems result from the environmental conditions associated with metal processing, such as heat, moisture, humidity, etc.
It is an object of embodiments of the invention to at least mitigate one or more of the problems of the prior art.